I am the "acting" IT person (very loose term) for our small company. I received this email yesterday. I am going to ignore it, but I was just curious how this could negatively effect me/us if I replied to it. I did some searching and found a few similar email reports on this, but no good explanations.
There is nothing that will harm you in responding, but you have to realise that this is a scam and they are trying to get you to respond in order to suck you into their trap. When they respond to your reply, they will ask you to open an attachment, send business details including bank info, or other things that will harm you.
When dealing with scams, unless you know what you are doing, it is best not to respond at all else you step onto their slippery slope. Remember, they do this for a living; you're just curious.